Punched adhesive tape for semiconductor, method of manufacturing lead frame with the adhesive tape, lead frame with the adhesive tape, and semiconductor device comprising the lead frame

ABSTRACT

A punched adhesive tape for semiconductor which is made by punching an adhesive tape comprising a base film and an adhesive layer provided on one or each side of the base film to mark the regions in the adhesive tape where contaminants or defects are contained; a method of producing an adhesive tape-bearing lead frame by punching the punched adhesive tape for semiconductor, with the parts containing the punched holes skipped over, and applying the adhesive tape pieces punched out from the punched adhesive tape for semiconductor to a lead frame; a semiconductor device fabricated by using the adhesive-bearing lead frame.

This application is a Divisional Application of Ser. No. 10/246,620,filed Sep. 19, 2002, now U.S. Pat. No. 7,273,654, which is aContinuation Application of application Ser. No. 09/462,943, filed Jan.18, 2000, now U.S. Pat. No. 6,523,446, which is a national stageapplication filed under 35 USC 371 of International Patent Application(PCT) No. PCT/JP98/03072, filed Jul. 9, 1998.

TECHNICAL FIELD

The present invention relates to punched adhesive tapes forsemiconductor particularly suitable for use in semiconductor deviceswherein semiconductor elements (chips) are bonded to lead frames, andalso relates to the production of adhesive tape-bearing lead frames, toadhesive tape-bearing lead frames and to semiconductor devicesfabricated using the adhesive tape-bearing lead frames.

BACKGROUND ART

In resin-molded semiconductor devices, adhesive tapes are now mainlyused as the adhesives for bonding semiconductor elements (chips) to leadframes.

If the adhesive tapes used for the above purpose contain contaminants ordefects, the reliability of semiconductor devices may be lowered. It istherefore necessary to inspect adhesive tapes for contaminants anddefects before applying the adhesive tapes to adherend lead frames, toavoid using adhesive tapes containing contaminants or defects.

A conventional, simple method of removing contaminants is to cut off theparts containing contaminants from adhesive tapes, to obtaincontaminants free adhesive tapes. This method however requires manyhands and is inefficient.

According to an alternative for preventing contamination, the regionscontaining contaminants are marked with seals, ink or the like, to avoidthese regions and use other regions for bonding. This method also needsimprovement since the adhesive tapes may be contaminated by the marking,causing the contamination of adherend chips.

DISCLOSURE OF INVENTION

The object of the present invention is to solve the above problems andto provide an adhesive tape for semiconductor which is excellent in workefficiency, a method of producing an adhesive tape-bearing lead frameusing the same, an adhesive tape-bearing lead frame, and a semiconductordevice fabricated by using the same. As a result of study to preventcontamination without cutting adhesive tapes nor contaminating them bymarking with seals or ink, we have hit upon an idea that punchingadhesive tapes at or in the vicinity of the regions containingcontaminants or defects is excellent in work efficiency and overcomesthe above problems, and we have consequently completed the presentinvention.

That is, the present invention provides a punched adhesive tape forsemiconductor, which is made of an adhesive tape comprising a base filmand an adhesive layer provided on one or each side of the base film, andis pierced with at least one punched hole which is made by punching theadhesive tape at or in the vicinity of a region where the adhesive tapecontains a contaminant or a defect.

The punched adhesive tape for semiconductor of the present invention issuitable particularly for bonding semiconductor chips to lead frames,and also has various other uses in the fabrication of semiconductordevices, for example, to bond semiconductor chips to TAB tapes.

The present invention further provides a method of producing an adhesivetape-bearing lead frame, comprising detecting the punched hole in thepunched adhesive tape for semiconductor, punching the punched adhesivetape for semiconductor, with a part thereof containing the punched holeskipped over, to punch out an adhesive tape piece from the punchedadhesive tape for semiconductor, applying the adhesive tape piece to alead frame, with one adhesive layer of the adhesive tape piece adheringto the lead frame.

The present invention further provides an adhesive tape-bearing leadframe produced by the above-described method.

The present invention further provides a semiconductor device fabricatedby using the adhesive tape-bearing lead frame.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a punched adhesive tape for semiconductor of anembodiment according to the present invention.

FIG. 2 is an expanded cross-sectional view of the punched adhesive tapefor semiconductor as shown in FIG. 1 taken in the direction of arrowsA-A.

FIG. 3 is a cross-sectional view of a semiconductor device of anembodiment according to the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter the punched adhesive tape for semiconductor of the presentinvention and the adhesive tape-bearing lead frame produced using thesame will be described in detail.

Exemplary films usable as the base film in the present invention includeinsulating heat resistant resin films, such as polyimide films,polyether-amide films, polyether-amide-imide films, polyether-sulfonefilms, polyether-ether-ketone films and polycarbonate films. The basefilm is preferably transparent. The thickness of the base film ispreferably 5 to 200 μm, more preferably 25 to 50 μm. Base films thickerthan 200 μm are disadvantageous to the production of thin resin-moldedsemiconductor devices, and base films thinner than 5 μm may lower thework efficiency in adhesive coating.

Non-limitative examples of adhesives usable to form the adhesive layerof the punched adhesive tape for semiconductor of the present inventioninclude adhesives comprising thermoplastic resins, such as aromaticpolyamides, aromatic polyesters, aromatic polyimides, aromaticpolyethers, aromatic polyether-amide-imides, aromatic polyester-imidesand aromatic polyether-imides, and adhesives comprising thermosettingresins, such as acrylic resins, epoxy resins and phenolic resins.

The thickness of each adhesive layer of the punched adhesive tape forsemiconductor of the present invention is generally 1 to 100 μm,preferably 5 to 50 μm, more preferably 10 to 25 μm.

For example, the adhesive tape to be used in the present invention forthe production of the punched adhesive tape for semiconductor isproduced by coating one or both sides of a base film with a varnish ofan adhesive dissolved in a solvent, and heating the coating to dry byremoving the solvent, to form an adhesive layer on one or each side ofthe base film. Adhesives comprising thermosetting resins are preferablysemi-cured, generally to B-stage, by the drying. The adhesive layer ispreferably transparent.

The adhesive tape may be provided with a peelable, transparentprotection film, such as polytetrafluoroethylene film,polyethyleneterephthalate film, release-treatedpolyethyleneterephthalate film, polyethylene film polypropylene film orpolymethylpentene film, on one or both adhesive layers. Adhesive tapesprovided with protection films may be punched together with theprotection films, or may be punched after the protection films arepeeled off. The thickness of the protection film is preferably 5 to 100μm, more preferably 10 to 50 μm.

The punching for making the punched holes piercing the punched adhesivetape for semiconductor of the present invention may be carried out byany method, for example by using a punching machine comprising atape-punching die and an air press capable of reciprocating the die.Contaminants and defects contained in the adhesive tape are removed bypunching the adhesive tape at the regions each containing a contaminantor a defect. However, it is not always necessary to punch out eachcontaminant or defective part completely so far as a region whichcontains a part of the contaminant or defect or is close to thecontaminant or defect is punched out. Even in such cases, adhesive tapepieces free of contaminants and defects can be obtained by punching thepunched adhesive tape for semiconductor, skipping over the punched holesand the neighborhood. When a punched hole is made in the vicinity of aregion containing a contaminant or a defect, the distance between thecenter of the punched hole and the region containing a contaminant or adefect is preferably 10 cm or less, more preferably 5 cm or less.

Herein, the term “contaminant” means a substance other than thematerials of the adhesive layer and of the base film, which lowers thereliability of semiconductor devices, such as a fine particle of aconductive substance and a dust particle, and the term “defect” meansthe part lacking the adhesive layer, the part where the thickness of theadhesive layer is not uniform, or the like, which causes bondingfailure.

The form of the punched hole is not limited, and is preferably circular.The punched hole may be of any size which does not cut the adhesivefilm. Preferred punched holes are circular holes of 0.5 to 10 mm, morepreferably 2 to 5 mm in diameter. Punched holes having a diameter ofmore than 10 mm may lower the tensile strength of the adhesive tape,causing break during practical use. Punched holes of less than 0.5 mm indiameter are difficult to make.

Punching adhesive tapes at the regions containing contaminants ordefects allows using long adhesive tapes as they are since contaminantsand defects can be removed without cutting the adhesive tapes. Acontamination inspection apparatus comprised of an adhesivetape-unwinding part, a CCD camera (charge-coupled device camera), apunching part and an adhesive tape-winding part enables a continuousprocess comprising unwinding an adhesive tape continuously from theadhesive tape-unwinding part, inspecting the appearance of the fedadhesive tape with the CCD camera, slowing down the adhesive tape tostop it upon the detection of a contaminant or a defect, punching theregion containing the contaminant or defect to make a punched hole atthe punching part, resuming unwinding, and finally winding the punchedadhesive tape.

FIG. 1 is a plan view of a punched adhesive tape for semiconductor of anembodiment according to the present invention, and FIG. 2 is an expandedcross-sectional view of the punched adhesive tape for semiconductor asshown in FIG. 1 taken in the direction of arrows A-A. As shown in thesefigures, a punched adhesive tape for semiconductor (1) consisting of abase film (2) and two adhesive layers (3, 3) provided, respectively, oneach side of the base film (2) is pierced with a circular punched hole(4), which is made by punching. The region of the material adhesive tapewhere a contaminant or a defect was contained has been removed bypunching the punched hole (4).

According to the method of the present invention, an adhesivetape-bearing lead frame is produced by detecting the punched hole in thepunched adhesive tape for semiconductor of the present invention,punching the punched adhesive tape for semiconductor, with a partthereof containing the punched hole skipped over, to punch out anadhesive tape piece from the punched adhesive tape for semiconductor,applying the adhesive tape piece to a lead frame, with one adhesivelayer of the adhesive tape piece adhering to the lead frame.

The lead frame to be used in the method of the present invention is notlimited in structure, and examples of usable lead frames include thosefor the use in COL (Chip on Lead) and LOC (Lead on Chip) semiconductordevices. Exemplary materials of the lead frame include 42 alloy andcopper alloy. The lead frame typically comprises inner leads, outerleads and bus bars, and one or more adhesive tape pieces may be appliedto any position selected depending on the structure of the lead frameand on the adherend, and when used to bond semiconductor chips,depending on the shapes of the semiconductor chips, the pad array on thechips, the design of the lead frame, etc.

The punched adhesive tape for semiconductor to be used in this methodpreferably has an adhesive layer on each side of the base film. When anadhesive film having only one adhesive layer is used, an adhesive layerneed be formed on the base film of the adhesive tape piece applied onthe lead frame, for example, by coating an adhesive, to bondsemiconductor chips thereon.

When the punched adhesive tape for semiconductor is provided with one ortwo protection films, the protection film on the adhesive layer whichadheres to the lead frame need be peeled off before punching. Theprotection film provided on the other side may be peeled off eitherbefore punching, or after punching and applying and before bondingadherend, such as semiconductor chips.

The form of the adhesive tape piece punched out from the punchedadhesive tape for semiconductor depends on the structure of the leadframe and on the adherend to be bonded to the lead frame. For example,when the adherend is a semiconductor chip, the form of the adhesive tapepiece depends on the shape of the semiconductor chip, the pad array onthe semiconductor chip, the design of the lead frame, or the like.

When the adhesive tape piece is applied to the lead frame, the leadframe is generally heated to 150 to 450° C. When the adhesive layers arethermosetting adhesive layers, at least the adhesive layer which doesnot contact the lead frame must not be completely cured but need remainsemi-cured. If completely cured, the adhesive layer cannot bond adherendsemiconductor chips any longer.

Preferably, the method of the present invention for producing anadhesive tape-bearing lead frame by using a punched adhesive tape forsemiconductor is carried out by employing a common process for applyingadhesive tapes to lead frames which comprises unwinding an adhesivetape, punching the adhesive tape (to punch out an adhesive tape piece tobe applied to a lead frame), applying the adhesive tape piece, andwinding the punched adhesive tape, and by adding thereto a step ofdetecting punched holes prior to the punching of the adhesive tapepiece. The detection of punched holes can be carried out visually, butpreferably by using a CCD camera, which permits automatic detection andimproves the work efficiency.

By winding (skipping) the punched adhesive tape for semiconductor acertain length, for example ±20 cm, preferably ±10 cm from the center ofeach punched hole in the direction of the length of the punched adhesivetape for semiconductor without punching the regions containing thedetected punched holes, it can be prevented to apply adhesive tapepieces containing contaminants or defects to lead frames. Further, sincethe regions of the material adhesive tape where contaminants or defectsare contained are marked by punching, there is no fear of contaminatingsemiconductor chips due to external causes, for example, due to themarking of contaminants and defects with seals or ink. The method of thepresent invention also reduces the work time since it permits using longadhesive tapes as they are without cutting, thereby reducing the numberof the exchanges of adhesive tapes during the work for applying adhesivetape pieces. That is, according to the method of the present invention,adhesive tape-bearing lead frames can be produced efficiently with goodyield.

The obtained adhesive tape-bearing lead frame has an advantage of lowproduction cost since the use of the punched adhesive tape forsemiconductor of the present invention improves the work efficiency,yield and productivity in the production of the adhesive tape-bearinglead frame. Also, the adhesive tape-bearing lead frame can decreasedefects in the semiconductor devices produced using them, reducing theproduction cost.

The semiconductor device of the present invention has no limitation inits structure so far as it is fabricated by using the adhesivetape-bearing lead frame of the present invention. FIG. 3 is across-sectional view of a semiconductor device of an embodimentaccording to the present invention, wherein the semiconductor chip (7)is mounted on the lead frame (5) comprising inner leads (51), outerleads (52) and bus bars (53). The inner leads (51) are connected withthe die pads of the semiconductor chip (7) by, for example, gold wires(8). The semiconductor device is molded with the sealing material (9).The semiconductor chip (7) is bonded to the lead frame (5) by theadhesive tape piece (6) by using an adhesive tape-bearing lead framewhich consists of the lead frame (5) and the adhesive tape piece (6)applied thereto.

For example, the semiconductor device of the present invention isproduced by bonding with heat and pressure a semiconductor chip to theadhesive tape piece applied to the adhesive tape-bearing lead frame ofthe present invention, curing (C-stage) the adhesive layers when theadhesive layers are made of thermosetting resin adhesives, connectingthe inner leads of the lead frame with the die pads of the semiconductorchip by wire bonding, followed by molding with a sealing material, suchas an epoxy resin sealing material.

The present invention will be described in more detail with reference tothe following Examples, which, however, are not to be construed to limitthe scope of the invention.

EXAMPLE 1

An adhesive tape (trade name: HM-122U, produced by Hitachi ChemicalCompany, Ltd., a three-layered adhesive tape: adhesive layer 25 μm thick(an aromatic polyether-amide-imide)/base film 50 μm thick (a polyimidefilm)/adhesive-layer 25 μm thick (an aromatic polyether-amide-imide)) 10m long by 9 mm wide was subjected to an appearance inspection using acontaminant (defect) inspector (trade name: SCANTEC-5000, produced byNagase Sangyo Co., Ltd.), which consists of an adhesive tape-unwindingpart, a CCD camera (trade name: TECEYE T15000H, produced by Excel Co.,Ltd.), a punching part and an adhesive tape-winding part. In the courseof the inspection, the contaminated or defective parts detected by theCCD camera or the neighborhoods thereof were punched out (punched hole:a circular hole of 3 mm in diameter) at the punching part. Thus apunched adhesive tape for semiconductor 10 m long was obtained withoutcutting the adhesive tape.

EXAMPLE 2

An adhesive tape (trade name: HM-122U, produced by Hitachi ChemicalCompany, Ltd.) 50 m long by 9 mm wide was subjected to an appearanceinspection using a contaminant (defect) inspector consisting of anadhesive tape-unwinding part, a CCD camera, a punching part and anadhesive tape-winding part. In the course of the inspection, thecontaminated or defective parts detected by the CCD camera or theneighborhoods thereof were punched out (punched hole: a circular hole of3 mm in diameter) at the punching part. Thus a punched adhesive tape forsemiconductor 50 m long was obtained without cutting the adhesive tape.

EXAMPLE 3

An adhesive tape (trade name: HM-122U, produced by Hitachi ChemicalCompany, Ltd.) 300 m long by 9 mm wide was subjected to an appearanceinspection using a contaminant (defect) inspector consisting of anadhesive tape-unwinding part, a CCD camera, a punching part and anadhesive tape-winding part. In the course of the inspection, thecontaminated or defective parts detected by the CCD camera or theneighborhoods thereof were punched out (punched hole: a circular hole of3 mm in diameter) at the punching part. Thus a punched adhesive tape forsemiconductor 300 m long was obtained without cutting the adhesive tape.

EXAMPLE 4

Using the punched adhesive tape for semiconductor produced in Example 1,an adhesive tape-bearing lead frame was produced as follows. A 42 alloylead frame comprising inner leads, outer leads and bus bars was used,and adhesive tape pieces (1 mm×6 mm) were applied to the inner leads andbus bars by a continuous process comprising unwinding the adhesive tape,detecting punched holes, punching out adhesive tape pieces, applyingthem to the lead frame, and winding the adhesive tape, wherein theadhesive tape pieces punched out from the adhesive tape forsemiconductor were applied to the lead frame by pressing them to thelead frame at 400° C. for 3 seconds under a pressure of 3 MPa. Thedetection of punched holes were carried out using a CCD camera, and ondetection of each punched hole, the adhesive tape was wound by 10 cm inthe direction of length without punching, to avoid punching a part of alength of ±5 cm from the center of the punched hole in the direction ofthe length of the adhesive tape, and to avoid applying the part to thelead frame. When all the adhesive tape pieces which were applied insequence to the lead frame were inspected, no contaminants nor defectswere observed.

EXAMPLE 5

Semiconductor chips (6.6 mm×15 mm×0.28 mm) were bonded to the adhesivetape-bearing lead frame produced in Example 4 on its side bearing theadhesive tape pieces by pressing for 3 seconds at 350° C. under apressure of 3 MPa. When the inner leads and the semiconductor chips wereconnected by wire bonding, no problem occurred. Then moldings with anepoxy resin sealing material (Trade name: CEL-920, produced by HitachiChemical Company, Ltd.) were carried out to produce semiconductordevices. After a moisture absorption test for 168 hours at 85° C. at arelative humidity of 85% followed by a reflow test in an IR furnace of amaximum temperature of 245° C., all the semiconductor devices workedproperly without any malfunction.

COMPARATIVE EXAMPLE 1

An adhesive tape (trade name: HM-122U, produced by Hitachi ChemicalCompany, Ltd.) of 10 m long by 9 mm wide was subjected to an appearanceinspection using a contaminant (defect) inspector consisting of anadhesive tape-unwinding part, a CCD camera and an adhesive tape-windingpart. In the course of the inspection, each time a contaminant or adefect was detected, the adhesive tape was cut off to remove a part of20 to 30 cm long containing the contaminant or defect. Thus two adhesivetapes for semiconductor of 3 m and 6.7 m in length were obtained.

COMPARATIVE EXAMPLE 2

An adhesive tape (trade name: HM-122U, produced by Hitachi ChemicalCompany, Ltd.) 50 m long by 9 mm wide was subjected to an appearanceinspection using a contaminant (defect) inspector consisting of anadhesive tape-unwinding part, a CCD camera and an adhesive tape-windingpart. In the course of the inspection, each time a contaminant or adefect was detected, the adhesive tape was cut off to remove a part of20 to 30 cm long containing the contaminant or defect. Thus three 10m-rolls, two 7 m-rolls and one 5 m-roll of adhesive tapes forsemiconductor were obtained.

COMPARATIVE EXAMPLE 3

An adhesive tape (trade name: HM-122U, produced by Hitachi ChemicalCompany, Ltd.) 300 m long by 9 mm wide was subjected to an appearanceinspection using a contaminant (defect) inspector consisting of anadhesive tape-unwinding part, a CCD camera and a tape winding part. Inthe course of the inspection, each time a contaminant or a defect wasdetected, the adhesive tape was cut off to remove a part of 20 to 30 cmlong containing the contaminant or defect. Thus three 50 m-rolls, four20 m-rolls, five 7 m-rolls and six 5 m-rolls of adhesive tapes forsemiconductor were obtained.

As to the adhesive tapes for semiconductor produced in Examples 1 to 3and Comparative Examples 1 to 3, the number of punched holes, the lengthper roll, the total length, the percentage of the tape loss uponapplying them to lead frames, and the number of exchanges of adhesivetapes during applying them to lead frames are shown in Table 1.

TABLE 1 Number of Number of punched Tape loss exchanges of holesLength/roll (%)*/roll adhesive tapes Example 1 1  10 m 15 once/10 mComp. 0  3 m (1 roll) 50 twice/10 m Example 1  6.7 m (1 roll) 22 Total:9.7 m Example 2 5  50 m 3 once/50 m Comp. 0  10 m (3 rolls) 15 sixtimes/50 m Example 2  7 m (2 rolls) 21  5 m (1 roll) 30 Total: 49 mExample 3 17 300 m 0.5 once/300 m Comp. 0  50 m (3 rolls) 3 18 times/300m Example 3  20 m (4 rolls) 7.5  7 m (5 rolls) 21  5 m (6 rolls) 30Total: 295 m *A tape loss of 1.5 m/roll in total of the lengths fromboth ends of each adhesive tape was caused by setting the adhesive tapeto the production apparatus.

Table 1 clearly shows that making punched holes in a material adhesivetape permits using an adhesive tape in good yield and improves workefficiency, compared with cutting the material adhesive tape.

INDUSTRIAL APPLICABILITY

Because the punched adhesive tape for semiconductor of the presentinvention is having contaminants and defects marked by punching,detecting the punched holes can prevent such defective parts of theadhesive tape from being applied to lead frames. Also there is noexternal factors of chip contamination, which are inherent in theconventional method of marking contaminants and defects with seals orink. Further, the punched adhesive tape for semiconductor reduces thework time since it enables using long adhesive tapes as they are withoutcutting, thereby decreasing the number of the exchanges of adhesivetapes during the work for applying adhesive tapes. That is, by using thepunched adhesive tape for semiconductor of the present invention,adhesive tape pieces can be applied to lead frames with high workefficiency and good yield.

Also the cost of producing the adhesive tape-bearing lead frame of thepresent invention using the punched adhesive tape for semiconductor isadvantageously low since the adhesive tape-bearing lead frame can beproduced efficiently with good yield and high productivity. Further, theadhesive tape-bearing lead frame reduces the malfunction of thesemiconductor devices fabricated by using it, thereby lowering theproduction cost.

1. A method for making an adhesive tape-bearing lead frame forfabricating semiconductor devices, comprising: providing a roll ofadhesive tape, the adhesive tape comprising a base film, an adhesivelayer provided on at least one side of the base film, and at least onehole punched completely through the base film and the adhesive layer ator in a vicinity of a region at which a contaminant or a defect had beendetected, the adhesive tape being wound into a roll; unwinding theadhesive tape from the roll; inspecting the unwound adhesive tape forpunched holes; cutting a length of adhesive tape having no punched holestherein; and adhering the adhesive layer of the cut length of adhesivetape to a lead frame.
 2. The method for making an adhesive tape-bearinglead frame for fabricating semiconductor devices according to claim 1,wherein the providing the roll of adhesive tape comprises: providing anadhesive tape comprising a base film and an adhesive layer provided onat least one side of the base film; inspecting the adhesive tape for atleast one of contaminants and defects; punching at least one holecompletely through the base film and the adhesive layer at or in avicinity of a region at which a contaminant or a defect is detected; andwinding the adhesive tape having at least one hole punched completelythrough the base film and the adhesive layer into a roll.